android:弹出对话框

一，代码：

xml:

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="162dp"
        android:layout_marginTop="96dp"
        android:layout_marginEnd="161dp"
        android:layout_marginBottom="587dp"
        android:text="对话框无按钮"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/button3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginStart="162dp"
        android:layout_marginTop="68dp"
        android:layout_marginEnd="161dp"
        android:layout_marginBottom="470dp"
        android:text="对话框有按钮"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button2" />
</androidx.constraintlayout.widget.ConstraintLayout>

java:

        //给按钮增加点击事件
        Button button2 = findViewById(R.id.button2);
        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                builder.setIcon(R.drawable.ic_launcher_background)
                        .setTitle("对话框")
                        .setMessage("hello,dialog")
                        .create()
                        .show();
            }
        });

        //给按钮增加点击事件
        Button button3 = findViewById(R.id.button3);
        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

                AlertDialog.Builder builder = new AlertDialog.Builder(MainActivity.this);
                builder.setIcon(R.drawable.ic_launcher_background)
                        .setTitle("对话框")
                        .setMessage("hello,dialog")
                        .setPositiveButton("确定", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                Log.d(TAG, getClass().getSimpleName() + " - 点击了确定");
                            }
                        })
                        .setNegativeButton("取消", new DialogInterface.OnClickListener() {
                            @Override
                            public void onClick(DialogInterface dialog, int which) {
                                Log.d(TAG, getClass().getSimpleName() + " - 点击了取消");
                            }
                        })
                        .create()
                        .show();

             }
        });

 

二，测试效果: